1. Is aiming in game too coarse? Then you need higher DPI.
2. Are quick movement being skipped (often referred to as, "negative acceleration")? If so, you need a mouse with a good sensor/firmware/driver for gaming.
3. Is not being able to arbitrarily remap button actions in some applications (even non-games) annoying? You need special software.
4. Don't like the feel of the small symmetrical mice everything comes with, these days? Find one with a shape that works for you.
There's nothing at all wrong with a plain jane OEM mouse (well, IMO, Gateway's are absolute trash, but aside from that...), as long as it works for you. Many gaming mice are indeed superior, and not only for gaming (gaming mice are popular choices for CAD users, both for the DPI and the configuration software, along with trackballs, and more funky many-axis stick-type input devices), but it's only worth it for you if you would take advantage of it.
Logitech's G400 should be available B&M. If you want to try a good gaming mouse out, it would be hard to find a better starting point, to sate your curiosity (not that I'm a biased Logtech fanboy, or anything...). If you like it, keep it, if not return it and get your money back, or return it and start finding others that do what you might want better.